title: Enzymatic assay for total plasma Cys.
abstract: Patients with vascular disease and end-stage renal disease have significantly higher concentrations of plasma total Cys (tCys) than do healthy individuals. Described here is a nonradioactive, precise, rapid and sensitive enzymatic colorimetric assay for tCys in plasma samples and is homogeneous in that it avoids separation methods. The tCys assay uses only the recombinant enzymes methionine alpha,gamma-lyase (rMETase) and S-adenosylhomocysteine hydrolase (rSAHH) cloned from Pseudomonas putida and Trichomonas vaginalis, respectively. The rSAHH traps homocysteine and the rMETase thereby produces H(2)S exclusively from Cys. The reaction product, H(2)S, is measured colorimetrically following its reaction with N,N-dibutylphenylenediamine (DBPDA). The procedure takes 3-4 h to complete.
authors.affiliation: AntiCancer, Inc., 7917 Ostrow Street, San Diego, CA 92111, USA.
authors.forename: Qinghong
authors.initials: Q
authors.lastname: Han
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hoffman
mesh_terms: D043383:Adenosylhomocysteinase; D013437:Carbon-Sulfur Lyases; D003124:Colorimetry / Q000379:methods*; D003545:Cysteine / Q000097:blood*; D005453:Fluorescence; D006801:Humans; D006862:Hydrogen Sulfide / Q000737:chemistry
chemical_list: D043383:Adenosylhomocysteinase; D013437:Carbon-Sulfur Lyases; C021558:L-methionine gamma-lyase; D003545:Cysteine; D006862:Hydrogen Sulfide